Optical-enhanced apparatus and method for illuminating printed circuit boards for inspection

Abstract

The apparatus includes: an illumination system having a planar printed circuit board, and a plurality of light producing elements mounted on the planar printed circuit board and divided into at least one area, a control system, wherein the light producing elements can be selected from at least one area and lighted to illuminate by the control system, and a flat thin lens system in front of and connected to the illumination system to focus the lights emitted from the light producing elements onto any position of the printed circuit board. The method applied to proposed apparatus includes steps of: (a) choosing a position, (b) setting the illumination conditions, (c) producing the required illumination through focusing the lights on the chosen position, (d) recording the image of chosen position, (e) displaying the image, (f) comparing the recording image with the referencing image, and (g) making a record of comparison.

What is claimed is:  
     
         1 . An apparatus for inspecting a printed circuit board, comprising: 
 an illumination system having a planar printed circuit board, and a plurality of light producing elements in which said plurality of light producing elements are arranged in planar high-density arrays mounted on and electrically connected to said planar printed circuit board, and said illumination system is divided into at least one area according to distances away from a central reference point of said illumination system;    a control system electrically connected to said illumination system, wherein said plurality of light producing elements of said illumination system are selected from at least one said area and lighted by said control system; and    a flat thin lens system having at least one flat thin lens, wherein said at least one flat thin lens is placed in front of and tightly connected to said illumination system to focus the lights emitted from said plurality of light producing elements onto any position of said printed circuit board.    
     
     
         2 . The apparatus according to  claim 1 , wherein said plurality of light producing elements are light emitting diodes.  
     
     
         3 . The apparatus according to  claim 1 , wherein said flat thin lens is a Fresnel Lens.  
     
     
         4 . The apparatus according to  claim 1 , wherein said apparatus further comprises a camera system having at least one camera to receive reflected lights of said printed circuit board originally emitted from said plurality of light producing elements.  
     
     
         5 . The apparatus according to  claim 4 , wherein said camera is mounted right behind one selected from a group consisting of said central reference point of said illumination system and a plurality of locations that are equally distanced from said central reference point respectively.  
     
     
         6 . The apparatus according to  claim 5 , wherein said at least one area can be divided into a central area and at least one peripheral area according to distances away from said central reference point of said illumination system.  
     
     
         7 . The apparatus according to  claim 6 , wherein each of said peripheral area can be further divided into at least one sub-area according to distances and directions away from said central reference point of said illumination system.  
     
     
         8 . The apparatus according to  claim 6 , wherein said control system controls each of said plurality of light producing elements of said area in one of on and off status and each of said camera of said camera system in one of on and off status to produce a combination of illumination conditions comprising a projecting direction, a projecting angle, and an illumination strength illuminated onto any position of said printed circuit board by said illumination system and to choose at least one said camera to record an image of a certain range centered by said position and illuminated by said illumination system when at least one said light producing element of at least one said area is lighted.  
     
     
         9 . The apparatus according to  claim 8 , wherein said certain range having a size decided by a size of sensor of said camera and a requirement of inspecting resolution.  
     
     
         10 . The apparatus according to  claim 8 , wherein said apparatus further comprises a display system having at least one display to show said image on a display screen.  
     
     
         11 . The apparatus according to  claim 8 , wherein said apparatus further comprises at least one microprocessor system to compare said image with a reference image record of said certain range to decide whether or not a difference existed and to be memorized in said microprocessor system.  
     
     
         12 . The apparatus according to  claim 1 , wherein said printed circuit board could be at any stage of a process for mounting electronic elements on said printed circuit board.  
     
     
         13 . A method using an apparatus having an illumination system with a plurality of light emitting diodes arranged in high-density arrays on a plane divided into at least one area, a flat thin lens system with at least one flat thin lens, a camera system with at least one camera, a control system, a microprocessor system with at least one microprocessor, and a display system with at least one display to inspect a printed circuit board, comprising steps of: 
 (a) Choosing a position on said printed circuit board;    (b) Setting a combination of illumination conditions comprising a projecting direction, a projecting angle, and an illumination strength according to a configuration of said printed circuit board in a certain range using said position as a reference center;    (c) Using said control system to let at least one of said plurality of light emitting diodes of at least one said area of said illumination system be lighted, and to focus emitted lights onto said position through said flat thin lens of said illumination system to produce said combination of illumination conditions on said position;    (d) Employing said control system to start at least one said camera to record a video image of said position illuminated by the illumination system according to said combination of illumination conditions of said position when at least one of said plurality of light emitting diodes of at least one said area of said illumination system is in “on” status;    (e) Displaying said video image of said position taken by at least one said started camera on a display screen of said display system according to said combination of illumination conditions of said position;    (f) Comparing a reference image record of said position stored in said microprocessor system with said video image of said position to decide whether or not a difference existed; and    (g) Recording whether or not a difference existed between said video image of said position and said reference image record of said position in said microprocessor system.    
     
     
         14 . The method according to  claim 13 , wherein said camera of said camera system is mounted right behind one selected from a group consisting of said central reference point of said illumination system and a plurality of locations equally distanced from said central reference point respectively.  
     
     
         15 . The method according to  claim 13 , wherein said area can be divided into a central area and at least one peripheral area according to distances away from said central reference point of said illumination system.  
     
     
         16 . The method according to  claim 13 , wherein each of said peripheral area can be further divided into at least one sub-area according to distances and directions away from said central reference point of said illumination system.  
     
     
         17 . The method according to  claim 13 , wherein said certain range having a size decided by a size of sensor of said camera and a requirement of inspecting resolution.  
     
     
         18 . The method according to  claim 13 , wherein said flat thin lens is a Fresnel Lens and is placed in front of and tightly connected to said light emitting diodes to focus the lights emitted from said plurality of light emitting diodes onto any position of said printed circuit board.  
     
     
         19 . The method according to  claim 13 , wherein said printed circuit board could be at any stage of a process for mounting electronic elements on said printed circuit board.